Electrical charge problem (need assurance on an answer)

Dry air will break down and generate a spark if the electric field exceeds about 3.0\times 10^6 N/C How much charge could be packed onto a green pea (diameter 0.81cm ) before the pea spontaneously discharges?

2. Relevant equations

E = kQ/r^2
Q = Er^2/ k <-------this is the equation to use I believe3. The attempt at a solution
(3*106)(3.81*10-3)2/8.988*109